Packer washout assembly

ABSTRACT

A packer washout assembly for removing debris from a well bore is disclosed. The packer washout assembly includes a tubing string positioned in the well bore and forming an annulus with the well bore. A packer is interposed in the tubing string and is sealable against the interior of the well bore. A packer washout sub is connected to an upper end of the packer. The packer washout sub includes a mandrel having at least one fluid flow port extending through a sidewall and a rupture disk positioned in the fluid flow port of the mandrel. The rupture disk is adapted to rupture upon the application of a predetermined pressure within the fluid passage of the mandrel so as to place the fluid passage in fluid communication with the annulus to permit fluid to pass through the fluid port from the mandrel to the annulus and thereby circulate fluid over the top of the packer so as to wash debris from the top of the packer.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates generally to an apparatus for washingdebris from a well bore, and more particularly, but not by way oflimitation, to an apparatus and method for washing debris from a packerset in a well bore to permit the packer to be released.

2. Brief Description of Related Art

Packers are downhole tools widely used in the completion of oil and gaswells to isolate and control producing and injected fluids. A variety ofpackers are known. Packers are often classified as either permanent orretrievable. A permanent packer is recovered from the well bore by usingmilling tools, while a retrievable packer is designed to be released andretrieved on the production tubing or on a workstring.

A concern of well operators when setting a retrievable packer is thepossibility of debris, such as sand, shale, or rust, settling on top ofthe packer and prohibiting the release of the packer. When this occursone of several things may be attempted to retrieve the packer from thewell bore. First, the tubing may be shot off just above the packerthereby permitting the majority of the tubing to be removed from thewell bore. Next, an operator may fish back on the tubing in attempt torelease the packer. Finally, if all the above fail, then the packer ismilled out, or the well may be abandoned.

Each of these procedures is time consuming and expensive. As such, aneed exists for a tool that may be used with a packer to allow debris tobe selectively removed from the packer when required. However, such animproved tool must also be cost efficient and substantiallymaintenance-free. It is to such a tool and method of use that thepresent invention is directed.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

FIG. 1 is a schematic illustration, partially in cross section, of apacker washout assembly constructed in accordance with the presentinvention.

FIG. 2 is a cross sectional view of a packer washout sub.

FIG. 3 is a cross sectional view of another embodiment of a packerwashout sub constructed in accordance with the present invention.

FIG. 4 is a cross sectional view of another embodiment of a packerwashout sub constructed in accordance with the present invention.

FIG. 5 is a schematic illustration, partially in cross section, ofanother embodiment of a packer wash out assembly constructed inaccordance with the present invention.

DETAILED DESCRIPTION OF THE INVENTION

Referring now to FIG. 1, a packer washout assembly 10 constructed inaccordance with the present invention for removing debris, such as sand,silt, shale, and rust, from the top of a packer 20 to permit the packerto be released is schematically illustrated. A well bore 12 is shown tobe lined with a casing 14 extending down from a wellhead 15. The casing14 provides a permanent borehole through which production operations maybe conducted. The casing 14 is affixed in the well bore 12 in aconventional manner, such as by cement (not shown), and is provided withperforations 16 open to a producing subterranean formation 17.

The packer washout assembly 10 includes a tubing string 18, a packer 20,and a packerwashout sub 22. The tubing string 18 provides fluidcommunication between the producing subterranean formation 17 and asurface 24 such that a reservoir fluid (not shown), for example oiland/or natural gas, is produced through the tubing string 18. The casing14 and the tubing string 18 define an annulus 26 which also providesfluid communication through the well bore 12.

The packer 20 is interposed in the tubing string 18 in a manner wellknown in the art. The packer 20 is commonly known as a retrievablepacker in that it is designed to be inserted in the casing 14 when in adeflated or relaxed condition, set so as to seal against the interiorwall of the well bore 12, and then released when it is desired to removethe tubing string 18 and the packer 20 from the well bore 12. Asmentioned above, release of the packer 20 may be hindered by theaccumulation of debris on top of the packer 20.

The packer washout sub 22 is interposed in the tubing string 18 byconnecting the packer washout sub 22 to the top of the packer 20. Asbest shown in FIG. 2, the packer washout sub 22 includes a mandrel 30having an upper end 32 adapted to be threadingly coupled to the tubingstring 18, a lower end 34 adapted to be threadingly coupled to the upperend 32 of the packer 20, and a sidewall 36 extending from the upper end32 to the lower end 34. The sidewall 36 defines a fluid passage 38extending from the upper end 32 to the lower end 34 so as to permitfluid flow between the tubing string 18 and the packer 20. The mandrel30 has at least one fluid port 40 extending through the sidewall 36;however, preferably, the mandrel 30 has a plurality of fluid ports 40.FIG. 2 shows one version where three fluid ports 40 are longitudinallyaligned from the lower end 34 to the upper end 32 of the mandrel 30along one side of the mandrel 30.

To close the fluid ports 40, a closure member 42 is positioned in eachof the fluid ports 40 of the mandrel 30 to close the fluid ports 40during normal well operations. The closure members 42 are illustrated asbeing rupture disks that are screwed into the fluid ports 40 orotherwise secured in the fluid ports 40. The rupture disks 42 areadapted to rupture upon the application of a predetermined pressurewithin the fluid passage 38 of the mandrel 30 so as place the fluidpassage 38 in fluid communication with the annulus 26 to permit fluid topass through the fluid port 40 from the mandrel 30 to the annulus 26 andthereby circulate fluid over the top of the packer 20 so as to washdebris from the top of the packer 20.

The rupture disks 42 selected to be positioned in the fluid ports 40must maintain their integrity under normal fluid production or injectionoperations. For example, if the tubing string 18 will be subject to 1000psi during production operations, a rupture disk rated to rupture at2,500 psi may be selected. On the other hand, if the tubing string 18 isbeing used for the injecting fluid into a formation, the tubing string18 may be subject to 5,000 psi. In this case, a rupture disk rated torupture at 10,000 psi may be selected.

FIGS. 3 and 4 illustrate other embodiments of a packer washout sub 22 aand 22 b, respectively. FIG. 3 shows the packer washout sub 22 a havingfour fluid ports 40 a arranged in a helical pattern about the sidewall36 of the mandrel 30 a. A rupture disk 42 a is positioned in each of thefluid ports 40 a. FIG. 4 shows the packer washout sub 22 b having fourfluid ports 40 b that are circumferentially spaced an equal distanceabout the mandrel 30 b. A rupture disk 42 b is positioned in each of thefluid ports 40 b.

The packer washout sub 22 is used in the event that the packer 20 failsto release due to the accumulation of debris (depicted in FIG. 1 by thereference numeral 48) such as sand, shale, silt, or rust, on top of thepacker 20. Upon determining that the packer 20 is stuck, a standingvalve 46 is landed on a seating nipple (not shown) to close off thetubing string 18 from below the packer washout sub 22. Next, the tubingstring 18 is pressurized with fluid, such as water, to a pressuresufficient to rupture the rupture disks 42. Upon the rupture disk 42rupturing, fluid communication between the fluid passage 38 of themandrel 30 and the annulus 26 is established to permit fluid to passfrom the mandrel 30 through the fluid port 40 and into the annulus 26.In the annulus 26, fluid is circulated through the debris, over the topof the packer 20, and finally to the surface 24 so as to carry thedebris to the surface 24 and thereby wash the debris from the top of thepacker 20. After the debris has been washed from the top of the packer20, the packer is released and the tubing string 18, along with thepacker washout sub 22 and the packer 20, is withdrawn from the well bore12.

FIG. 5 illustrates the use of a packer washout sub 22 in a tubing string18 a. The tubing string 18 a includes a packer 20 a and a plug 48. Thetubing string 18 provides fluid communication between producingsubterranean formation 50 and a surface 52 such that a reservoir fluid(not shown), for example oil and/or natural gas, is produced through thetubing string 18 a. A casing 14 a is affixed in a well bore 12 a in aconventional manner, such as by cement (not shown), and is provided withperforations 54 open to the producing subterranean formation 50. It willbe noted that the producing subterranean formation 50 is above thepacker 20 a. As such, the tubing string 18 a is provided withperforations 56 to permit fluid passing from the formation 50 to passinto the tubing string 18 a.

In the situation where the packer 20 a fails to release and the tubingstring 18 a is perforated above the packer 20 a, the perforations 56 arefirst sealed prior to pressuring the tubing string 18 a for the purposeof rupturing the rupture disks 42. The perforations 56 may be sealed byinserting balls 58 into a stream of fluid injected into the tubingstring 18 a at the surface 52. The balls 58 will lodge in theperforations 56 and thereby seal the perforations 56. Upon determiningthat the perforations 56 are sealed by an increase in fluid pressure,the fluid pressure in the tubing string 18 a is further increased to apressure sufficient to rupture the rupture disks 42. Upon the rupturingof the rupture disks 42, fluid is circulated through the debris(depicted in FIG. 5 by the reference numeral 60), over the top of thepacker 20 a, and finally to the surface 52 so as to carry the debris tothe surface 52 and thereby wash the debris from the top of the packer 20a. After the debris has been washed from the top of the packer 20 a, thepacker 20 a is released and the tubing string 18 a, along with thepacker washout sub 22 and the packer 20 a, is withdrawn from the wellbore 12 a.

From the above description it is clear that the present invention iswell adapted to carry out the objects and to attain the advantagesmentioned herein as well as those inherent in the invention. Whilepresently preferred embodiments of the invention have been described forpurposes of this disclosure, it will be understood that numerous changesmay be made which will readily suggest themselves to those skilled inthe art and which are accomplished within the spirit of the inventiondisclosed and as defined in the appended claims.

1. A packer washout assembly for removing debris from a well bore,comprising: a tubing string positioned in the well bore and forming anannulus with the well bore; a packer interposed in the tubing string andsealable against the interior of the well bore, the packer having anupper end and a lower end; a packer washout sub comprising: a mandrelhaving an upper end connected to the tubing string, a lower endconnected to the upper end of the packer, and a sidewall extending fromthe upper end to the lower end, the sidewall defining a fluid passageextending from the upper end to the lower end, the mandrel having atleast one fluid flow port extending through the sidewall; and a closuremember positioned in the fluid flow port of the mandrel, the closuremember adapted to open upon the application of a predetermined pressurewithin the fluid passage of the mandrel so as to place the fluid passagein fluid communication with the annulus to permit fluid to pass throughthe fluid port from the mandrel to the annulus and thereby circulatefluid over the top of the packer so as to wash debris from the top ofthe packer.
 2. The packer washout assembly of claim 1 wherein themandrel includes a plurality of fluid ports, each fluid port has aclosure member positioned therein.
 3. The packer washout assembly ofclaim 1 wherein the mandrel includes a plurality of fluid flow portsextending through the sidewall, the fluid ports longitudinally axiallyaligned from the lower end to the upper end of the mandrel, each fluidflow port having a closure member positioned therein.
 4. The packerwashout assembly of claim 1 wherein the mandrel includes a plurality offluid flow ports extending through the sidewall, the fluid portsarranged in a helical pattern about the sidewall of the mandrel, eachfluid flow port having a closure member positioned therein.
 5. Thepacker washout assembly of claim 1 wherein the mandrel includes aplurality of fluid flow ports extending through the sidewall, the fluidports circumferentially spaced an equal distance about the mandrel, eachfluid flow port having a closure member positioned therein.
 6. A packerwashout assembly for removing debris from a well bore, comprising: atubing string positioned in the well bore and forming an annulus withthe well bore; a packer interposed in the tubing string and sealableagainst the interior of the well bore, the packer having an upper endand a lower end; a packer washout sub comprising: a mandrel having anupper end connected to the tubing string, a lower end connected to theupper end of the packer, and a sidewall extending from the upper end tothe lower end, the sidewall defining a fluid passage extending from theupper end to the lower end, the mandrel having at least one fluid flowport extending through the sidewall; and a rupture disk positioned inthe fluid flow port of the mandrel, the rupture disk adapted to openupon the application of a predetermined pressure within the fluidpassage of the mandrel so as to place the fluid passage in fluidcommunication with the annulus to permit fluid to pass through the fluidport from the mandrel to the annulus and thereby circulate fluid overthe top of the packer so as to wash debris from the top of the packer.7. The packer washout assembly of claim 6 wherein the mandrel includes aplurality of fluid ports, each fluid port having a rupture diskpositioned therein.
 8. The packer washout assembly of claim 6 whereinthe mandrel includes a plurality of fluid flow ports extending throughthe sidewall, the fluid ports longitudinally axially aligned from thelower end to the upper end of the mandrel, each fluid flow port having arupture disk positioned therein.
 9. The packer washout assembly of claim6 wherein the mandrel includes a plurality of fluid flow ports extendingthrough the sidewall, the fluid ports arranged in a helical patternabout the sidewall of the mandrel, each fluid flow port having a rupturedisk positioned therein.
 10. The packer washout assembly of claim 6wherein the mandrel includes a plurality of fluid flow ports extendingthrough the sidewall, the fluid ports circumferentially spaced an equaldistance about the mandrel, each fluid flow port having a rupture diskpositioned therein.
 11. A method for removing debris from the top of apacker sealed against a well bore, comprising: producing fluid through atubing string positioned in the well bore, the tubing string forming anannulus with the well bore, the tubing string having a packer interposedtherein, the packer sealed against the interior of the well bore and thepacker having an upper end and a lower end, the tubing string furtherhaving a packer washout sub, the packer washout sub comprising: amandrel having an upper end connected to the tubing string, a lower endconnected to the upper end of the packer, and a sidewall extending fromthe upper end to the lower end, the sidewall defining a fluid passageextending from the upper end to the lower end, the mandrel having atleast one fluid flow port extending through the sidewall; and a rupturedisk positioned in the fluid flow port of the mandrel; sealing thetubing string; and pressurizing the tubing string to a sufficientpressure to rupture the rupture disk of the packer washout sub so as toplace the fluid passage of the mandrel in fluid communication with theannulus to permit fluid to pass through the fluid port from the mandrelto the annulus and thereby circulate fluid over the top of the packer soas to wash debris from the top of the packer.
 12. A method for removingdebris from the top of a packer sealed against a well bore, comprising:providing a tubing string in the well bore so that the tubing stringforms an annulus with the well bore, the tubing string having a packerinterposed therein, the packer sealed against the interior of the wellbore and the packer having an upper end and a lower end, the tubingstring further having a packer washout sub, the packer washout subcomprising: a mandrel having an upper end connected to the tubingstring, a lower end connected to the upper end of the packer, and asidewall extending from the upper end to the lower end, the sidewalldefining a fluid passage extending from the upper end to the lower end,the mandrel having at least one fluid flow port extending through thesidewall; and a rupture disk positioned in the fluid flow port of themandrel; sealing the tubing string; and pressurizing the tubing stringto a sufficient pressure to rupture the rupture disk of the packerwashout sub so as to place the fluid passage of the mandrel in fluidcommunication with the annulus to permit fluid to pass through the fluidport from the mandrel to the annulus and thereby circulate fluid overthe top of the packer so as to wash debris from the top of the packer.